Photographic processing liquids and method of producing photographic images

ABSTRACT

CARBAZIC ACID, BICARBAMIC ACID, OR A WATER-SOLUBLE SALT THEREOF IS USED IN THE PRODUCTION OF PHOTOGRAPHIC REVERSAL IMAGES OR DIRECT POSTITIVES, BOTH BLACK AND WHITE AND COLORED. THE ADDITIVE CAN BE ADDED TO THE DEVELOPING LIQUID FOR THE DEVELOPMENT STAGE OF THE REVERSAL PROCESS, OR BY WAY OF ANOTHER PROCESSING LIQUID FOR WETTING THE MATERIAL BEING PROCESSED PRIOR TO THE DEVELOPMENT WHERE THE REVERSAL PROCESS UTILZES PLURAL DEVELOPMENT STAGES THE ADDITIVE IS PREFERABLY APPLIED BY WAY OF THE FINAL DEVELOPING LIQUID OR ANOTHER PROCESSING LIQUID APPLIED PRIOR TO THE FINAL DEVELOPMENT STEP.

United States Patent 3,565,620 PHOTOGRAPHIC PROCESSING LIQUIDS AND METHOD OF PRODUCING PHOTOGRAPHIC IMAGES Jozef Frans Willems, Wilrijk, Gerard L. Vanreusel, Hove, and Camille A. Vandeputte, Mortsel, Belgium, assignors to Gevaert-Agfa N.V., Mortsel, Belgium, a Belgian company No Drawing. Filed Oct. 24, 1967, Ser. No. 677,763 Claims priority, application Great Britain, Oct. 24, 1966, 47,633/ 66 Int. Cl. G03c 5/50 US. Cl. 96-55 37 Claims ABSTRACT OF THE DISCLOSURE Carbazic acid, bicarbamic acid, or a water-soluble salt thereof is used in the production of photographic reversal images or direct positives, both black and white and colored. The additive can be added to the developing liquid for the development stage of the reversal process, or by way of another processing liquid for wetting the material being processed prior to the development stage. Where the reversal process utilizes plural development stages the additive is preferably applied by way of the final developing liquid or another processing liquid applied prior to the final development step.

This invention relates to photographic processing liquids for the treatment of light-sensitive silver halide materials and to methods for the production of photographic reversal or direct positive images wherein such processing liquids are used.

It has been found that photographic processing liquids to which carbazic acid, bicarbamic acid and/or at least one water-soluble salt thereof has been added, are particularly suited for being applied in photographic processes instead of an overall exposure. The processing liquids according to the invention are especially suitable for being used in the generally known method of producing reversal images and in a particular method of producing photographic direct positive images, which latter method will be described hereafter detailedly, in both cases instead of an overall re-exposure.

A photographic processing liquid to which carbazic acid, bicarbamic acid and/or a water-soluble salt thereof has been added not only exerts a good fogging action whereby it forms developable specks in a light-sensitive silver halide material that is treated therewith, but moreoverand this is very unexpectedis particularly keepable so that after several weeks it can still be used with about the same good results.

Carbazic acid and its water-soluble salts can be prepared eg as described in Berichte 37, 4523 (1904). Examples of water-soluble salts of carbazic acid are: the hydrazine salt of carbazic acid and the sodium salt of carbazic acid. An example of a water-soluble salt of bicarbamic acid is the potassium salt of bicarbamic acid. The terms carbazic acid and bicarbamic acid include the substituted compounds too.

Carbazic acid, bicarbamic acid and/or their watersoluble salts usually are added to the processing liquid in an amount comprised between about 1 g. and about g., preferably between 5 g. and 20 g. per litre. The choice to which processing liquid these compounds have to be added depends upon the type of photographic process. Since, however, the treatment in a photographic processing liquid according to the present invention replaces an overall exposure, it is obvious to carry out said treat- 'ice' ment at that stage at which otherwise the overall exposure occurred, or at an earlier stage if possible in the whole of the different subsequent steps of the process concerned. Preferably, however, the fogging compounds for use according to the present invention are incorporated into the developing liquid that normally would have been applied after an overall exposure.

The present invention also relates to methods for the manufacture of photographic reversal black-and-white images comprising the consecutive steps of image-wise exposing a light-sensitive silver halide reversal material, developing the exposed silver halide material, eliminating the developed silver image and developing the remaining unexposed silver halide, carbazic acid, bicarbamic acid and/ or at least one water-soluble salt thereof being added to the developing liquid for the latter development and/ or to another processing liquid with which the light-sensitive material is wetted before said latter development and after the said first development.

The method for the manufacture of photographic reversal colour images according to the present invention comprises the consecutive steps of image-wise exposing a light-sensitive silver halide reversal material, developing the exposed silver halide in a black-and-white developing liquid, developing the remaining unexposed silver halide with a colour developing liquid in the presence of a colour coupler, carbazic acid, bicarbamic acid and/ or at least one water-soluble salt thereof having been added to the colour developer and/or to a processing liquid with which the light-sensitive material is wetted before the colour development and after the black-and-white de- "velopment, and finally eliminating the developed silver.

The method of producing direct-positive images according to the present invention which in the whole further part of the description will be explained detailedly comprises the steps of image-wise exposing a light-sensitive material that comprises a layer of a silver halide emulsion that mainly forms internal latent image and little external latent image as defined hereinafter,

developing the light-sensitive material thus exposed with an energetic surface developer, carbazic acid, bicarbamic acid and/ or at least one water-soluble salt thereof having been added to this developer and/or to another processing liquid with which the light-sensitive material is wetted before development.

In order to stabilize the photographic direct positive image obtained after the developing step the material is generally fixed e.g. in a usual fixing solution such as a thiosulphate solution and washed, whereupon the said material may be dried or glazed.

This embodiment of the present invention provides a method of producing direct positive images of good quality in a rapid and simple way. This method is particularly suitable for producing continuous tone direct positive images but is also appropriate for reproducing line originals.

The light-sensitive material of use for carrying out this embodiment of the present invention generally comprises a support, for instance a paper support or a hydrophobic film support that is either transparent or not, to which the light-sensitive silver halide emulsion layer is applied, if need be by means of an appropriate subbing layer.

The silver halide emulsion used is of the type in which the latent image is formed mostly or entirely internally in the grains, that is to say an emulsion only few or none of the exposed grains of which are developable to silver by a developing solution which cannot act as a developer for latent image inside the grains i.e. a so-called surface developer, such as the following developing solution:

G. p-Hydroxyphenylglycine 10 Sodium carbonate (cryst.) 100 Water to 1000 ccs.

and the exposed grains of which are well developable to silver by a developing solution which acts as a developer for latent image inside the grains, i.e. a so-called internal developer such as the following developing solution:

G. Hydroquinone 15 Monomethyl-p-aminophenol sulphate 15 Anhydrous sodium sulphite 50 Potassium bromide 10 Sodium hydroxide 25 Sodium thiosulphate (cryst.) 20

Water to 1000 ccs.

By a silver halide emulsion that mainly forms internal latent image and little external latent image there is more particularly meant a silver halide emulsion, a test layer of which, upon exposure to a light intensity scale for a fixed time between and 1 second and development for 3 minutes at 20 C. in the above internal developer, exhibits a maximum density at least 3 times and preferably at least times the maximum density obtained when an identical test layer of the said silver halide emulsion is equally exposed and then developed for 4 minutes at 20 C. in the above surface developer. Said preference for a maximum density of at least 5 times as large particularly applies to the case the method is applied to the production of black-and-white direct positive images. When the method is applied to the production of colour images wherein the formed silver image is eliminated as will be explained detailedly further in the description, 3 times said maximum density will sufiice in order to obtain good results.

Silver halide emulsions that meet the above requirement and hence are suitable for being employed in this embodiment of the invention are generally not or only slightly chemically ripened silver halide emulsions, since the extent of the surface latent image forming ability increases with the degree of chemical ripening.

Silver chlorobromide emulsions comprising at least 20 mole percent of silver bromide and pure silver bromide emulsions have proved to be specially suitable. When these emulsions comprise a certain amount of silver iodide, often not more than 5 mole percent relative to the total amount of silver halide, they are just as well suitable. Washed as well as unwashed silver halide emulsions may be used.

The silver halide emulsions for use in this embodiment of the invention are generally gelatino silver halide emulsions. However, the gelatin may at least partly be replaced, e.g. by another protein, a hydrophilic not proteinaceous colloid, e.g., a polyvinylpyrrolidone or a synthetic polymeric substance applied from an aqueous dispersion, i.e. a latex, e.g., a polyethyl acrylate latex. The presence of such other binders often has also a favourable photographic efiect on the formation of the direct positive image. For instance, the addition of the polyvinylpyrrolidone and of said polyethyl acrylate latex in most cases increases the maximum density of the direct positive image.

The light-sensitive silver halide emulsions may be prepared according to all known and conventional techniques for emulsion preparation. A method according to which emulsions are prepared, which have proved to be particularly suitable for the purpose of this embodiment of the present invention, is the so-called conversion method. According to this method a more soluble silver halide is converted in a less soluble silver halide e.g., a silver chloride emulsion is converted in the presence of water-soluble bromide and occasionally iodide, the amounts of which are adapted in view of the final composition aimed at, into a silver chlorobromide or a silver emulsion, which may occasionally comprise small amounts of silver iodide. This conversion is carried out preferably very slowly by several consecutive steps. Another technique according to which emulsions with an increased intern latent image sensitivity may be obtained is described in the British patent specification 1,011,062. For further specifications of the nature and preparation of light-sensitive silver halide emulsion layers suitable for use according to this embodiment of the present invention reference is made to the specific examples given below.

A considerable improvement of this embodiment of the present invention can be obtained by incorporating at least one compound that sets free iodide ions in aqueous medium and/or at least one compound that sets free bromide ions in aqueous medium into the light-sensitive material in eifective contact with the silver halide emulsion layer. By in effective contact is meant that the said compounds are provided in the light-sensitive material on a place from which they can act upon the silver halide emulsion layer at the appropriate moment i.e. during the development. They may be incorporated into whatever composing layer of the light-sensitive material that is in water-permeable relationship with the lightsensitive silver halide emulsion layer; however, they are preferably present in the light-sensitive silver halide emulsion layer itself. They may be incorporated into the lightsensitive material by soaking the latter before or after the image-wise exposure in an aqueous composition containing them, e.g., the energetic surface developer itself, or by adding them to the coating composition of a particular layer of the light-sensitive material.

The idea of incorporating into the light-sensitive material the compound(s) setting free iodide ions in an aqueous medium and/or the compound(s) setting free bromide ions in an aqueous medium, by adding them to the energetic surface developer or to a preceding processing liquid for treating the light-sensitive material after the image-wise exposure, is the subject of another patent application. Said United Kingdom patent application 47,- 630/ 66 filed Oct. 24, 1966 by Gevaert-Agfa N.V. relates to a slightly different method of producing direct positive images.

As said above the compounds that set free iodide ions or bromide ions are preferably incorporated into the light-sensitive silver halide emulsion layer itself. They are generally added to the light-sensitive silver halide emulsion after the silver halide has been precipitated and occasionally converted.

For carrying out this embodiment of the invention the compounds that set free iodide ions or bromide ions can be applied in greatly varying concentrations i.e. in concentrations that depend on the nature of the compounds used and of the light-sensitive silver halide emulsion. However, their concentration is mostly comprised between 0.01 and 20 g., preferably between 0.1 and 5 g. per mole of silver halide.

The high maximum density of the direct positive image obtained according to this embodiment of the invention is due to the presence of said compounds setting free iodide or bromide ions. The best results i.e. the highest densities, can be attained when using simultaneously compounds that set free iodide ions and compounds that set free bromide ions, although good results are also attained when using one of both kinds of compounds alone, particularly those setting free iodide ions.

Suitable compounds setting free iodide ions are among others water-soluble iodides, inorganic as well as organic iodides, organic compounds with labile iodine atom, onium chloroiodates, and molecular iodine and its addition products, e.g. with polyvinylpyrrolidone, With'polyoxyalkylenes and their derivatives, or with quaternary ammonium compounds.

The idea of using molecular iodine and/or its addition products as compounds setting free iodide ions is the subject of another United Kingdom patent application 47,629/ 66 filed Oct. 24, 1966 by Gevaert-Agfa N.V. relating to a slightly different method of producing direct-positive images.

Silver iodide sols are less suited for being used as compositions releasing iodide ions. Up to now they only have shown some suitability when having been incorporated in a large concentration into the fluid silver halide emulsion shortly before the latter is applied to a support.

Suitable inorganic iodides are for instance, calcium iodide, ammonium iodide, lithium iodide, magnesium iodide, potassium iodide, sodium iodide, barium iodide, cadmium iodide, and zinc iodide.

Suitable organic iodides are for instance the iodides having the following structural formulae:

tetramethylammonium iodide,

tetraethylammonium iodide-3-diiodine,

CH3 H C(CH 1I INH2 I" 1,1,1dodecyldimethylhydrazinimum(1+)iodide,

OH CH: 1

1-methyl-8-hydroxy-quinolinium iodide,

OHa l @I 1-methyl-2-iodo-quinolinium iodide,

H3O CH3 1,2,3 ,4-tetrahydro-8-hydroxy-1, l-dimethyl-quinolinium iodide, -Q

benzyltriphenylphosphonium iodide,

I13 CH3 oIn).-

113 C C H3 S,S'-bis-(dimethyD-hexamethylene-1,6-disulphonium iodide,

3,S-dimorpholino-dithiolium iodide, and

diphenyl-iodonium iodide.

Organic compounds with labile iodine atom which have proved to be suitable for use according to the invention are for instance mono-iodo-acetic acid and 4-iodo-butane sulphonic acid potassium salt.

Finally, as regards the onium chloroiodate there may be referred to Belgian patent specification No. 515,895; examples of suitable onium chloroiodates are i.a.

COOCHa I012 trimethyl- (o-methoxycarbonyl -anilinium dichloroiodate, and

@ @j Q Q benzyltriphenyl-phosphonium dichloroiodate Suitable compounds setting free bromide ions are among others inorganic and organic bromides such as ammonia bromide, lithium bromide, sodium bromide, potassium bromide, magnesium bromide, calcium bromide, barium bromide, cadmium bromide and zinc bromide as inorganic bromides and tetraethyl ammonium bromide and ethyl pyridinium bromide as organic bromides. Organic compounds with labile bromine atom such as monobromoacetic acid are also suitable for being used in the present process as compounds setting free bromide ions.

In a first step for the preparation of the direct positive image the light-sensitive material is image-wise exposed to the original to be reproduced. This exposure can be either a high-intensity exposure such as flash exposure or a normal-intensity exposure such as daylight exposure as well as a low-intensity exposure such as an exposure by means of a printer or an exposure of still lower intensity, the exposure-time being dependent on the sensitivity of the light-sensitive material for the direct positive image formation which sensitivity according to the present invention may be a camera speed as well as a lower sensitivity.

In a further step of the direct positive image formation according to this embodiment of the present invention the image-wise exposed light-sensitive material is soaked with an energetic surface developer for instance by conducting the material through a tray containing such developer. The developer of use in this embodiment of the invention must be a surface developer i.a. a developer that contains no or at least no effective amount of solvents for silver halide. In this case by solvents for silver halide there are meant particularly strong solvents for silver halide such as water-soluble thiocyanates, thiosulphates, ammonia, etc. Indeed, compounds that may be considered to be but very weak solvents for silver halide, such as sodium sulphite in case the silver halide is silver bromide,

silver chlorobromide or silver bromoiodide, may be present in the developer.

Further the developer has to be an energetic developer. The high energy required can be realized by taking, e.g. one or more of the following measures:

using a developer with relatively high pH value,

working at an elevated temperature,

using a developer wherein the concentration of the various compounds present is relatively high,

incorporating developing activators such as cyclohexylamine, phenylhydrazine, polyethylene glycols and derivatives into the developer, and

omitting, at least for the greater part, to add restrainers such as potassium bromide to the developer.

The choice of the developing substances too determines the energy of the developer. Examples of suitable developing substances are among others the combination of 1- phenyl-S-pyrazolidinone with hydroquinone and the combination of monoethyl-p-aminophenol sulphate with hydroquinone. In general there may be said that the more energetic the developer is the better the result obtained will be.

For carrying out the method of the present invention the developing substances may partly or even wholly be incorporated into the light-sensitive material. This incorporation step may take place at the preparation stage of the material or later on by means of a processing liquid with which the light-sensitive material is wetted before the development of the direct positive image occurs. In doing so, the energetic surface developer can be reduced to a mere alkaline liquid which is substantially free from developing substances. Such an alkaline aqueous liquid is also called activator" and offers the considerable advantage of being usable for a longer time, i.e. of being exhausted not so rapidly.

The developer (occasionally activator) and/or some other processing liquid may also be applied in an amount accurately measured out and just sufl'icing for the processing of one single sheet of light-sensitive material. One speaks then of a single-use bath. The advantage thereof is that aging and contamination of the bath composition are avoided.

Carbazic acid, bicarbamic acid and/ or at least one water-soluble salt thereof have to be added to the energetic surface developer and/ or to a preceding processing liquid for the light-sensitive material. Those compounds cause the formation of a latent direct positive image that will be developable by the energetic surface developer. The best results are obtained with carbazic acid, bicarbamic acid, and/ or at least one water-soluble salt of carbazic acid and/or of bicarbamic acid added to the developer itself. When using in this embodiment of the present invention another processing liquid incorporating carbazic acid, bicarbamic acid and/or a salt thereof this liquid is preferably employed just before the development step and in any case after the exposure step. The pH of the liquid to which have been added the carbazic acid, bicarbamic acid and or salts thereof, preferably is fairly high and in most cases amounts to at least about 10. A preliminary separate processing liquid containing carbazic acid, bicarbamic acid, and/or salts thereof, in addition may comprise other ingredients such as one or more of the ingredients that otherwise would have been incorporated into the developer. Wetting of the light-sensitive material by means of the liquid composition to which have been added carbazic acid, bicarbamic acid and/or at least one water-soluble salt thereof can occur in any way, such as by soaking or by wetting only one side of the light-sensitive material, e.g. by means of a lick roller, by spreading a paste, contained in a pod, or by spraying.

The concentration, in which carbazic acid, bicarbamic acid and/or the water-soluble salts thereof are incorporated into the processing liquid, and suitable water-soluble salts by means of which the present embodiment of the invention is carried out have been mentioned hereinbefore.

According to the method of the invention the fog caused normally by the fogging compounds for use according to the present invention can also be produced partially by an overall exposure of the light-sensitive material to actinic light of weak intensity during development. Especially for the preparation of colour images reference mostly is given to a combined use of the fogging compound(s) with such an overall exposure. More particulars about the execution of such overall exposure can be found in the published Dutch patent applications 6605891 and 6605890.

For one skilled in the art it was not obvious at all to try to replace at least partially the overall exposure step during development in the process according to the United States patent applications 546,528 and 546,640, both filed May 2, l966-Which step is very specific as it cannot be carried out before or after the developmentby the use of very specific fogging agents in at least one of the proc essing liquids.

As already stated above, the direct positive images obtained according to this embodiment of the present invention show very high maximum densities and have sufficiently low minimum densities.

This minimum density can still be lowered by incorporating a fog-inhibiting compound into the light-sensitive material of use for carrying out this embodiment of the present invention. This fog-inhibiting compound must be present in effective contact with the silver halide emulsion layer. By in effective contact is meant that the fog-inhibiting compound is provided in the light-sensitive material on a place from which it can act upon the silver halide emulsion layer at the appropriate moment, in this case during the soaking of the light-sensitive material with the developer. The fog-inhibiting compound is preferably incorporated in the silver halide emulsion layer itself, but may also be present in another water-permeable non-lightsensitive layer of the light-sensitive material such as a covering layer or an intermediate layer, from which it is dissolved by the developer liquid and diffuses to the lightsensitive layer. It is even possible to incorporate considerable amounts of the fog-inhibiting compound into the developer liquid.

The fog-inhibiting compounds give rise to a lowering of the minimum density of the direct positive image even when present only in small amounts. They are very eflicient when applied in the common fog-inhibiting amounts. The best results i.e. the most clear minimum densities are however attained when using the fog-inhibiting compounds in amounts larger than the common fog-inhibiting amounts i.e. in amounts that normally are not applied to light-sensitive materials since with such amounts the lightsensitive material would be too strongly desensitized. What is surprising now is that these large amounts of fog-inhibiting compound do not lower the direct-positive image sensitivity of the light-sensitive material but in most cases even enhance it and also do not prevent the formation of a direct positive image with good maximum density. Specific data about the concentrations in which the fog-inhibiting compounds are generally employed and give the best results for the process according to the present invention can hardly be given since these concentrations are widely divergent according to the nature of the fog-inhibiting compound and the kind of silver halide emulsion layer used. For instance in the case of a silver bromide emulsion layer considerably less fog-inhibiting compound must be used than in the case of a silver chlorobromide emulsion layer for attaining almost equivalent results.

Fog-inhibiting compounds of the following classes have proved to be particularly suitable for being applied in this embodiment of the invention:

The class of the heterocyclic thione compounds such as:

4-phenyl-A -1,2,4-triazoline-5 -thione, 3-phenyl-A -1,2,4-triazoline-5-thione,

1-methyl-2-tetrazoline-S-thione,

1-phenyl-2-tetrazoline-S-thione,

1-( l-naphthyl -2-tetrazoline-5-thione,

1-(Z-naphthyl)-2-tetrazoline-5-thione,

1- (9-anthryl)-2-tetrazoline-5-thione,

1-( 3,4-dichlorophenyl)-2-tetrazoline-5-thione,

1-( o-methoxy-phenyl)-2-tetrazoline-5-thione,

1-(o-biphenyl)-2-tetrazoline-5-thione,

1- (p-biphenyl -2-tetrazoline-5-thione,

l- 2-naphthyl -4,4,6-trimethyll ,2,3 ,4-tetrahydropyrimidine-Z-thione;

The class of the aromatic and aliphatic mercapto com pounds such as:

2-mercapto-ethyl carbanilate;

The class of the benzotriazoles such as:

5-(3-phenylureido)-lH-benzotriazole; and

The class of the fused oxo-compounds containing at least two nitrogen atoms such as:

5 -nonyl-7-oxo-4,7-dihydro-s-triazolo-[ l ,5 -a] -pyrimidine,

and 2-methyl-4-hydroxypyrimido-[1,2-a]-benzimidazole.

It will be understood that these classes are intended to refer also to the tautomeric structures of said compounds and to salts of said compounds or occasionally of said tautomeric structures. Mixtures of two or more fog-inhibiting compounds may also be employed.

In carrying out this embodiment of the invention the maximum or minimum density of the direct positive image can still be improved and the characteristics of the lightsensitive material can be altered by using all kinds of ingredients which are generally known in the art of emulsion preparation and some of which will be set out specifically hereinafter.

Most of these ingredients are preferably incorporated into the light-sensitive material itself, in effective contact with the silver halide emulsion layer and favourably in the latter layer itself. Many of these ingredients, however, may be incorporated into the energetic surface developer with the same favourable result. Combinations of two or more of said ingredients, of course, may also be used.

Among the said ingredients may be mentioned some binders for at least partially replacing gelatin as a binder for the silver halide grains and referred to already above in the description, further optical sensitizers and moistening agents such as polyalkylene glycols, i.a. polyethylene glycols, sulphonated fatty acids, saponine and the like. The presence of optical sensitizers and of polyalklene glycols in the silver halide emulsion layer in most cases has a favourable effect on the maximum density of the direct positive image. Still further ingredients are mentioned later on in the description.

This embodiment for producing direct-positive images is not restricted to black-and-white photography; it may also be applied for the preparation of direct positive colour images by carrying out the development in an energetic colour developer in the presence of a colour coupler and by bleaching away the silver developed. The light-sensitive material, of course, may be a multilayer colour material each layer of which absorbs a particular part of the spectrum and for which layers appropriate colour couplers are provided. In addition to their developing or coupling action many colour developing compounds and colour couplers exert an advantageous efiFect on the mechanism of the direct positive image production itself in that they contribute to a higher maximum and/ or a lower minimum density.

The following examples illustrating the processes of the present invention.

EXAMPLE 1 A usual light-sensitive photographic black-and-white 10 First it is developed for about 5 minutes in the following developing liquid the pH of which has been adjusted at 10.5:

G. Hydroquinone 2 Monomethyl-p-amino-phenol hemisulphate 4 Potassium bromide 2 Sodium carbonate 40 Sodium sulphite 40 Potassium thiocyanate 5 Water to make 1000 ccs.

Then the film material is treated for about 5 minutes in the following bleaching bath:

Potassium dichromate-S g. Strong sulphuric acid (d.=l,85)l0 ccs. Water to make 1000 ccs.

After rinsing for some minutes in water the film material is treated for 5 minutes in a clearing bath of the following composition:

Sodium sulphitel00 g. Water to make 1000 ccs.

After rinsing again for some minutes the film material is treated for about 2 minutes in the following processing liquid whose pH has been adjusted at 11:

Carbazic acidl0 g. Potassium carbonate-40 g. Water to make 1000 ccs.

The film material is then developed for 6 minutes in the following developing liquid whose pH has been adjusted to 11:

G. Hydroquinone 5 Monomethyl-p-aminophenolhemisulphate 1 Sodium sulphite 40 Sodium carbonate 30 Potassium bromide 0.5

Water to make 1000 ccs.

Finally the film material is rinsed and dried. A reversal image of very good quality is obtained.

EXAMPLE 2 Example 1 is repeated, but the treatment in the processing liquid containing carbazic acid, which preceded the second development is omitted, and the carbazic acid is added to the second developing liquid in an amount of 10 g. per litre.

EXAMPLE 3 A usual photographic light-sensitive colour reversal silver halide film material is image-wise exposed and then processed at 20 C. in the following way.

First it is developed for 5 minutes in the following de veloping liquid the pH of which has been adjusted to 10.5:

Water to make 1000 ccs.

Then the film material is treated for 2 minutes in a stop bath of the following composition:

G. Acetic acid 10 Sodium acetate 5 reversal silver halide film material 1s image-wlse exposed and then processed at 20 C. in the following way.

ll After rinsing for some minutes the film material is treated for 2 minutes in the following processing liquid Whose pH has been adjusted to 11:

G. Carbazic acid Potassium carbonate 40' Water to make 1000 ccs.

Then the film material is developed for 8 minutes in the following colour developing liquid whose pH has been adjusted to 10.5:

G. Diethyl-p-phenylenediamine hydrochloride 4 Sodium sulphite 2 Potassium bromide 1 Sodium carbonate 40 Water to make 1000 ccs.

After a new treatment for some minutes in the above stop bath and rinsing, the film material is treated for about 8 minutes in the following bleaching bath whose pH has been adjusted to 4.5:

G. Potassium hexacyanoferrate (III) '30 Potassium bromide Water to make 1000 ccs.

After rinsing the film material is fixed for 5 minutes in a solution of 200 g. of sodium thiosulphate in 1 litre of water, rinsed and dried.

A reversal colour image of very good quality is obtained.

EXAMPLE 4 EXAMPLE 5 A gelatino silver bromide emulsion that mainly forms internal latent image and little external latent image is prepared through conversion of a silver chloride emulsion by very slowly adding to said emulsion whilst stirring a 35% aqueous potassium bromide solution in an amount that is 70% higher than the amount theoretically necessary for converting all the silver chloride. The emulsion is then kept for 1 hour at 60 C. After the emulsion has been chilled and allowed to gel for 6 hours the emulsion is noodled. The noodles are washed for 1 hour with water (10 litres of water per minute). By heating the washed noodles a liquid silver bromide emulsion is obtained containing 50 g. of gelatin and 0.4 mole of silver bromide per kg.

To this liquid emulsion potassium iodide is added as follows: to a first part of the emulsion 6 ccs. of a 5% aqueous potassium iodide solution are added per kg., to a second part 10 ccs. of such solution are added per kg. and to a third part ccs. of such solution are added per kg.

Each of the light-sensitive emulsions obtained is coated, practically immediately after the addition of the potassium iodide solution, on a baryta-coated paper support of 130 g./sq.m. in such a way that an amount of silver halide equivalent to 4 g. of silver nitrate is present per sq.m. of light-sensitive material.

The emulsion layer of each of the materials is overcoated with a conventional hardened gelatin antistress layer.

The three silver halide materials obtained are further treated in a completely identical way. Each material is imagewise exposed for fl see. through a step-wedge by means of a flash exposure of 130 lux sec. Then each material is developed for 4 min. at 20 C. in a surface developer of the following composition:

G. Hydroquinone 15 1-phenyl-3-pyrazolidinone 1 Sodium carbonate (anhydrous) 30 Sodium sulphite (anhydrous) 40 Carbazic acid 9 Water up to 1000 ccs. The pH is adjusted to 11.

Each of the light-sensitive materials is then fixed, rinsed and dried in the conventional way.

A direct positive image of the original is obtained in each of the three materials. The three images all have a low minimum density and a high maximum density which is the higher the more potassium iodide has been incorporated into the light-sensitive material. As compared with a direct positive image obtained in the same manner but with a light-sensitive material containing no potassium iodide, the direct positive images obtained according to the method of the invention as described in this example, show a much higher maximum density and practically the same minimum density.

EXAMPLE 6 Example 5 is repeated but carbazic acid is omitted from the developer, and after the image-wise exposure and just before the development for 4 minutes each of the light-sensitive materials is dipped into the following solution at 20 C. the pH of which has been adjusted to 11:

G. Potassium carbonate 30 Carbazic acid i 9 Water to make 1000 ccs.

A somewhat lower maximum density is obtained than in the corresponding images of 'Example 5.

EXAMPLE 7 Example 5 is repeated as far as the light-sensitive material, in which the highest amount of potassium iodide has been incorporated is concerned. However, immediately after having incorporated said potassium iodide and before coating 5 ccs. of a 5% solution in ethanol of 1- (o-methoxyphenyl)-2-tetrazoline-5-thione are also added to the silver halide emulsion.

The direct positive image obtained has a minimum density lower than that obtained in the corresponding material of Example 5 where no antifoggant has been incorporated into the light-sensitive material. Its maximum density has practically not been changed as compared with the material comprising no antifoggant.

EXAMPLE 8 Example 7 was repeated, but carbazic acid was replaced by a same amount of hydrazine salt of carbazic acid. The obtained results were about the same as those obtained in Example 7.

EXAMPLE 9 Example 7 was repeated but with the following surface developer (activator) comprising a fogging compound:

G. Anhydrous sodium carbonate 30 Anhydrous sodium sulphite 40 Hydrazine salt of carbazic acid 9 Water up to 1000 ccs.

The pH was adjusted to 11.

The silver halide emulsion layer contained moreover per sq.m. 1 g. of hydroquinone, 250 mg. of 1-phenyl-3- pyrazolidinone, 1 g. of formaldehyde bisulphite and 0.1 g. of potassium metabisulphite.

A direct positive image of good quality was obtained in this way.

We claim:

1. A method of producing photographic reversal blackand-white images comprising the steps of image-wise exposing a light-sensitive silver halide reversal material, developing the exposed silver halide, eliminating the developed silver image and developing the remaining unexposed silver halide, characterized in that carbazic acid, bicarbamic acid and/or at least one water-soluble salt of carbazic acid and/or of bicarbamic acid has been added to the developing liquid for the latter development and/ or to another processing liquid with which the lightsensitive material is wetted before the said latter development and after the said first development.

2. A method of producing photographic reversal colour images comprising the steps of image-wise exposing a light-sensitive silver halide reversal material, developing the exposed silver halide in a black-and-white developing liquid, developing the remaining unexposed silver halide in a colour developing liquid in the presence of a colour coupler, and eliminating the developed silver, characterized in that carbazic acid, bicarbamic acid and/or at least one water-soluble salt thereof has been added to the colour developing liquid and/or to another processing liquid with which the lightsensitive material is wetted before the colour development and after the black-andwhite development.

3. A method of producing photographic direct positive images that comprises the steps of:

image-wise exposing a light-sensitive material, that comprises a layer of a silver halide emulsion that mainly forms internal latent image and little external latent image as defined in the description, and developing the light-sensitive material thus exposed with an energetic surface developer, carbazic acid, bicarbamic acid, and/or at least one water-soluble salt thereof having been added to this developer and/or to another processing liquid with which the light-sensitive material is wetted before development.

4. A method according to claim 3, wherein at least one compound setting free iodide ions in an aqueous medium and/or at least one compound setting free bromide ions in an aqueous medium has been incorporated into the light-sensitive material in efiective contact with the silver halide emulsion layer.

5. A method according to claim 4, wherein a watersoluble inorganic iodide has been incorporated into the light-sensitive material as a said compound setting free iodide ions in an aqueous medium.

6. A method according to claim 3, wherein the lightsensitive material comprises a fog-inhibiting compound in efiective contact with the silver halide emulsion layer.

7. A method according to claim 4, wherein the lightsensitive material comprises a fog-inhibiting compound in eflfective contact with the silver halide emulsion layer.

8. A method according to claim 7, wherein the fog-inhibiting compound is present in an amount substantially larger thanllfog-inhibiting amounts.

9. A method according to claim 7, wherein the foginhibiting compound is a fog-inhibiting compound of the class of the heterocyclic thione compounds, of the class of the aromatic or aliphatic mercapto compounds, of the class of the benzotriazoles or of the class of the fused oxo-compounds containing at least two nitrogen atoms.

10. A method according to claim 7, wherein the foginhibiting compound is 1(o-methoxy-phenyl) 2 tetrazoline-S-thione.

11. A method according to claim 4, wherein the silver halide emulsion is not or only slightly chemically ripened.

12. A method according to claim 4, wherein the silver halide emulsion is a silver chlorobromide emulsion comprising at least 20 mole percent silver bromide or a silver bromide emulsion, which emulsions may contain at most 5 mole percent of silver iodide relative to the total amount of silver halide.

13. A method according to claim 12, wherein the silver halide emulsion has been prepared by the so-called conversion method.

14. A method according to claim 4, wherein a polyalkylene glycol is present in the light-sensitive material in effective contact with the silver halide emulsion layer.

15. A method according to claim 4, wherein the silver halide emulsion comprises polyvinylpyrrolidone.

16. A method according to claim 4, wherein the silver halide emulsion comprises a latex.

17. A method according to claim 4, wherein the pH of the processing liquid whereto carbazic acid, bicarbamic acid, and/or at least one water-soluble salt thereof has been added amounts to at least about 10.

18. A method according to claim 3, wherein the lightsensitive material is developed with an energetic colour developer in the presence of a colour coupler and the silver developed is bleached away.

19. A method according to claim 18, wherein several silver halide emulsion layers constitute a multilayer colour material, each layer of which absorbs a particular part of the spectrum and for each of which layers an appropriate colour coupler is provided.

20. A method according to claim 18, wherein at least one compound setting free iodide ions in an aqueous medium and/ or at least one compound settin free bromide ions in an aqueous medium has been incorporated into the light-sensitive material in effective contact with the silver halide emulsion layer.

21. A method according to claim 20, wherein a watersoluble inorganic iodide has been incorporated into the light-sensitive material as a said compound setting free iodide ions in an aqueous medium.

22. A method according to claim 18, wherein the lightsensitive material comprises a fog-inhibiting compound in effective contact with the silver halide emulsion layer.

23. A method according to claim 20, wherein the lightsensitive material comprises a fog-inhibiting compound in effective contact with the silver halide emulsion layer.

24. A method according to claim 23, wherein the foginhibiting compound is present in an amount substantially larger than fog-inhibiting amounts.

25. A method according to claim 23, wherein the foginhibiting compound is a fog-inhibiting compound of the class of the heterocyclic thione compounds, of the class of the aromatic or aliphatic mercapto compounds, of the class of the benzotriazoles or of the class of the fused oxocompounds containing at least two nitrogen atoms.

26. A method according to claim 23, wherein the foginhibiting compound is l-(o-methoxy-phenyl) 2 tetrazoline-S-thione.

27. A method according to claim 20, wherein the silver halide emulsion has not or only slightly been chemically ripened.

28. A method according to claim 20, wherein the silver halide emulsion is a silver chlorobromide emulsion comprising at least 20 mole percent silver bromide or a silver bromide emulsion, which emulsions may contain at most 5 mole percent of silver iodide relative to the total amount of silver halide.

29. A method according to claim 28, wherein the silver halide emulsion has been prepared by the so-called conversion method.

30. A method according to claim 20, wherein the silver halide emulsion comprises a latex.

31. A method according to claim 29, wherein the latex is a polyethyl acrylate latex.

32. A method according to claim 20, wherein the pH of the processing liquid whereto carbazic acid, bicarbamic acid and/or at least one water-soluble salt thereof has been added, amounts to at least about 10.

33. A method according to claim 20, wherein the lightsensitive material during development is overall exposed with actinic light of weak intensity.

34. A method according to claim 4, wherein at least a part or the total amount of the compound(s) of the group consisting of compounds setting free iodide ions in aqueous medium and compounds setting free bromide ions in aqueous medium are added to the energetic surface developer or to a preceding processing liquid for treating the light-sensitive material after the image-wise exposure.

35. A method according to claim 20, wherein at least a part or the total amount of the compound(s) of the group consisting of compounds setting free iodide ions in aqueous medium and compounds setting free bromide ions in aqueous medium are added to the energetic surface developer or to a preceding processing liquid for treating the light-sensitive material after the image-wise exposure.

36. A method according to claim 4, wherein at least part or the total amount of the developing substance(s) is present in the light-sensitive material in effective contact with the silver halide emulsion layer.

37. A method according to claim 20, wherein a least part or the total amount of the developing substance(s) is present in the light-sensitive material in effective contact with the silver halide emulsion layer.

References Cited FOREIGN PATENTS 4/1965 Great Britain 9615 OTHER REFERENCES Berichte 37, 4523-4524 (1904) Germany.

NORMAN G. TORCHIN, Primary Examiner A. T. SURO PICO, Assistant Examiner US. Cl. X.R. 

